Would you envisage a thermal instability issue if I mounted the output transistors and the Vbe multiplier only on the main heatsink? The drivers would have separate heatsinks. Finally, what is the maximum (safe) supply voltage that can be applied please?

Thanks Currentflow. There is a sneaky advantage of having the drivers on main heat sink and that is higher hfe. However if they are mounted on separate heat sink there is better thermal stability. +-50 unless you change the vas area transistors and out put transistors. Its a dissipation issue ( you could even give them baby heat sinks )and max break down voltage issue.

Still trying to come up with a part number for a nice fuse holder. All I keep finding are simple fuse holder ends that mount on the board but they just look cheap. I would much rather have them in a holder with a base to it. I know that someone posted a picture of their amp that was the first one partially assembled with fuse holders but I am not finding that thread right now to ask that person what they were. No reason to make this thing look cheap.

Mr.Harrison I would be more than glad to built you friend an amp,,I,m very sorry to hear that he can,t do it himself. But remember I,m very slow I canm only use 1 hand So if your friend can wait a little I,ll gladly do it. Evette